In Proverbs 26:4-5 it seems like we have a contradiction.  It's actually quite the opposite.   We read that we aren't to answer a fool according to his folly but as his folly deserves.  The key to it is to understand the context, which is that the non-believer, the person who says there's no such thing as absolute right-and-wrong, is always making moral proclamations. This means that people are consistently contradicting themselves and we shouldn't join them in the charade but challenge the central point behind their moral assertions.  We should ask them: by what standard are you judging?  That's the key.